Question

I thought that Ruby only allowed single inheritance besides mixin. However, when I have class Square that inherits class Thing, Thing in turn inherits Object by default.

class Thing
end

class Square < Thing
end

Doesn’t this represent multiple inheritance?

Answer 1

I think you are taking the meaning of multiple inheritance in a wrong way. Probably what you have in mind as multiple inheritance is like this:

class A inherits class B
class B inherits class C

If so, then that is wrong. That is not what multiple inheritance is, and Ruby has no problem with that. What multiple inheritance really means is this:

class A inherits class B
class A inherits class C

And you surely cannot do this in Ruby.